JP2017513605A - Apparatus and method for tomosynthesis imaging - Google Patents

Abstract

The present invention is an apparatus for tomosynthesis imaging, said apparatus being configured to generate a binary mask based on a geometric three-dimensional model of a scanned object. An image capture module (102) configured to scan a series of two-dimensional projection images of the object, and during reconstruction of a three-dimensional image volume from the series of scanned two-dimensional projection images And an image processing module (103) configured to apply the generated binary mask and to limit the range of the reconstructed image volume to the range of the geometric model.

Description

  The present invention relates to an apparatus and method for imaging technology. In particular, the present invention relates to an apparatus and method for tomosynthesis imaging.

  In tomosynthesis, the 3D image volume is reconstructed from an angular range smaller than 180 ° (eg, typically 10 ° -60 ° in human breast tomosynthesis) using X-ray projection. Due to the limited angular range of the setup, the spatial range of the object under examination in the main X-ray direction cannot be accurately reconstructed by known image reconstruction techniques.

  EP 2,101,648 B1 describes a method and apparatus for generating tomosynthesis three-dimensional X-ray images, in which a plurality of digital two-dimensional X-ray projection images are limited using an X-ray source and a digital X-ray detector. Recorded from the inspection object at different projection angles, so-called fan artifacts are removed by the binary three-dimensional mask, and the projection image data of the first two-dimensional X-ray image recorded at the first projection angle and the second projection It is determined from the projection image data of the second two-dimensional X-ray image recorded at the corner.

  FR 2,978,911 A1 describes a method of irradiating a part of the human body, for example a human breast, with low energy radiation in order to obtain a low energy image with an imaging detector. The body part is located between the radiation source and the detector. Since the composite medical image is generated from the low and high energy images by the controller, the tissue of the body part can be displayed in the composite medical image. A system for collecting and processing a medical image of a body including an implant is further described.

  There is a need to improve digital image processing for tomosynthesis imaging.

  These needs are met by the subject matter of the independent claims. Further exemplary embodiments are evident from the dependent claims and the following description.

  An aspect of the invention is an apparatus for tomosynthesis imaging, a mask generator module configured to generate a binary mask based on a geometric three-dimensional model of a scanned object; An image capture module configured to scan a series of two-dimensional projection images; and applying a binary mask generated during reconstruction of a three-dimensional image volume from a series of scanned two-dimensional projection images And an image processing module configured to limit the range of the reconstructed image volume to the range of the geometric model.

  A further aspect of the invention relates to an apparatus for tomosynthesis imaging and an X-ray medical imaging system comprising a mammography apparatus.

  A further aspect of the invention is a method for tomosynthesis imaging, generating a binary mask based on a geometric three-dimensional model of a scanned object; a series of two-dimensional projection images of the object Applying a generated binary mask to the scanned series of two-dimensional projection images to limit the extent of each of the reconstructed image volumes to the dimensions of the geometric model Regarding the method.

  The present invention provides an approach that overcomes the occurrence of image artifacts outside the object due to a limited angular range. Since true attenuation cannot be recovered, such artifacts also appear in the object, for example as low frequency intensity fluctuations.

  The present invention advantageously solves this problem by applying a mask image generated by binary tomosynthesis reconstruction.

  The present invention uses these X-ray spectral information to advantageously identify X-rays by non-zero line integral values.

  The present invention allows multi-energy projection data to be decomposed into basic material images, such as absorption due to photoelectric and Compton effects. This advantageously allows a quantitative representation of the length of each ray through the object if the volume can be broken down into a mixture of two substances. This is the case for mammographic volumes because breast tissue is most often a mixture of fat and glandular tissue. Degradation can then be expressed as height and gland.

  If multi-energy projection data is not available, the local height can also be estimated from conventional single energy projection data for those locations where one tissue type, preferably adipose tissue dominates. Height information for other positions can then be obtained by interpolation.

  Since height or length information through such a volume is available from images taken at different angles, a binary image volume describing the outline of the scanned object can be reconstructed. In short, this problem is generally non-deterministic polynomial time hard, NP-hard for short, but can be mitigated by introducing geometric preliminary information such as relevance, smoothness and convex constraints. it can. Further boundary conditions are also known: The maximum length through the breast is given by the compression height and is constant over a large area between the breasts. Furthermore, the skin-line can be depicted in detail precisely in that the X-ray is parallel to the skin.

This type of geometric height model information can be represented as a binary image. This binary image can then be used as a mask in an actual tomosynthesis configuration, allowing a better reconstruction of the object range in the main x-ray direction, thus improving tomosynthesis,
-Allows rendering of breast contours for all slices (ie in 3D) and improved background masking,
-Reduced strength towards the edge of the breast (no need for post-processing thickness equalization / compensation) is avoided,
-The resulting image artifacts on the object being imaged, for example inside and outside the human breast being imaged, are reduced.

  In other words, the present invention advantageously proposes generating a three-dimensional mask image using length information from spectral image decomposition. This removes image artifacts and overcomes the need for thickness equalization.

  This method can be used for tomosynthesis images and effectively “looks behind the breast” at an angle outside the coverage of a tomosynthesis scan, otherwise at an angle that is impossible due to limited tomographic angles. The tomographic angle or tomographic angle is the tube movement amplitude expressed in degrees.

  The terms “scanned object” or “imaged object” as used in the description of the invention refer to, for example, mammography or any other that uses high or low energy x-rays to examine a human breast. Relates to the object to be scanned or any other object or part of the human body that is investigated by this process and used as a diagnostic and screening tool.

  The terms “energy-resolved x-ray image” or “spectral x-ray image” may be understood as an image acquired using any type of x-ray technique, eg, energy-resolved photon counting detector and classification methodology. In use, more than two substances can be efficiently separated. Specifically, this applies when a contrast agent containing a K-absorption edge is present in the object in the energy range of interest. This separation is made possible through the use of a recently developed energy-resolved photon counting detector with multiple thresholds, allowing simultaneous measurement of x-ray attenuation at multiple energies.

  The binary mask is based on a geometric three-dimensional model of the scanned object mask that represents the three-dimensional, possibly bent, spatial extent of the object.

  According to an exemplary embodiment of the present invention, the mask generator module is configured to generate a binary mask based on a geometric model derived from laser scanning of an object. This can be combined with intensity information from the projected image.

  This advantageously provides improved matching of the geometric 3D model with the scanned object.

  According to an exemplary embodiment of the present invention, the mask generator module applies a geometric model derived from image analysis of at least one two-dimensional projection image of a series of two-dimensional projection images to be scanned of an object. And is configured to generate a binary mask based thereon.

  This advantageously provides improved matching of the geometric 3D model with the scanned object.

  According to an exemplary embodiment of the present invention, the mask generator module is configured to determine a geometric model of the object based on an intensity profile of at least one two-dimensional projection image of the object.

  This advantageously provides improved matching of the geometric 3D model with the scanned object.

  According to an exemplary embodiment of the present invention, the image capture module can collect energy-resolved x-ray images and the geometric model is obtained from a quantitative high-resolution obtained from spectral material decomposition of energy-resolved two-dimensional projection images. Derived from the model.

  According to an exemplary embodiment of the present invention, the mask generator module is configured to generate a binary mask using the object thickness value measured by the mechanical compression unit.

  According to an exemplary embodiment of the present invention, the image processing module is configured to apply the generated binary mask during a reconstruction procedure of a series of scanned 2D projection images.

  A computer program that performs the method of the present invention may be stored on a computer-readable medium. Computer-readable media are floppy disk, hard disk, CD, DVD, USB (Universal Serial Bus) storage device, RAM (Random Access Memory), ROM (Read Only Memory) and EPROM (Erasable Programmable Read Only Memory). There may be. The computer readable medium may be a data communication network, such as the Internet, that allows program code to be downloaded.

  The methods, systems, and devices described herein may be implemented as software in a digital signal processor (DSP), microcontroller, or any other side processor, or as a hardware circuit within an application specific integrated circuit (ASIC). May be. The present invention may be implemented in digital electronic circuitry, or computer hardware, firmware, software, or a combination thereof, eg, new hardware dedicated to handle the methods described herein.

  The present invention can be implemented for the use of image reconstruction in a variety of image processing applications and aims to demonstrate the usefulness of this transformation for image modification and segmentation tasks.

  A more complete appreciation of the invention and its attendant advantages will be more clearly understood by referring to the following schematic drawings, which differ in dimensions.

FIG. 2 shows a schematic diagram of an apparatus for tomosynthesis imaging according to an exemplary embodiment of the present invention. FIG. 3 shows a schematic flow chart diagram of a method for tomosynthesis imaging according to an exemplary embodiment of the present invention. 1 shows a schematic diagram of an X-ray medical imaging system having a mammography apparatus and an apparatus for tomosynthesis imaging according to an exemplary embodiment of the present invention. FIG. The two-dimensional projection image for demonstrating this invention is shown. 4 shows another two-dimensional projection image for explaining the present invention. 4 shows another two-dimensional projection image for explaining the present invention. 1 shows backprojection for illustrating the present invention. Fig. 4 shows another backprojection for explaining the present invention. Fig. 4 shows another backprojection for explaining the present invention.

  The examples in the drawings are purely diagrammatic and are not intended to provide scaling relationships or size information. In different drawings, similar or identical elements are provided with the same reference numerals. In general, identical parts, units, entities or steps are provided with the same reference signs in the detailed description.

  FIG. 1 shows a schematic diagram of an apparatus for tomosynthesis imaging according to an exemplary embodiment of the present invention.

  The apparatus 100 for tomosynthesis imaging may include a mask generator module 101 configured to generate a binary mask based on a geometric three-dimensional model of the scanned object.

  The apparatus 100 may further include an image capture module 102 configured to scan a series of two-dimensional projection images of the object.

  In addition, the apparatus applies a binary mask that is generated during reconstruction of a 3D image volume from a series of scanned 2D projection images, and reconstructs the range of the reconstructed image volume in a geometric model. An image processing module 103 configured to limit the range may be included.

  FIG. 2 shows a schematic flowchart diagram of a method for tomosynthesis imaging according to an exemplary embodiment of the present invention.

  The method is visualized with respect to the block diagram. The method may comprise three steps S1, S2 and S3.

  As a first step of the method, a step S1 is executed which generates a binary mask based on a geometric model of the object to be scanned.

  As a second step of the method, step S2 of scanning a series of two-dimensional projection images of the object is performed. For example, if the geometric model of the object to be scanned is based on a generated projection image that is scanned in step S2 for scanning the sequence, step S2 for scanning the sequence includes step S1 for generating a binary mask. May be executed prior to. For example, as illustrated in the schematic flowchart diagram of FIG. 2, if the binary mask is generated from the object thickness value measured by the mechanical compression unit, the scanning step S2 is the step S1 of generating the binary mask. It may be executed subsequently.

  As a third step of the method, a step S3 is performed in which the generated binary mask is applied to a series of two-dimensional projections to be scanned to limit the extent of each image to the dimensions of the geometric model.

  According to exemplary embodiments of the present invention, these steps may be performed simultaneously, divided into multiple operations or tasks, or repeated.

  FIG. 3 shows a schematic diagram of an X-ray medical imaging system having a mammography apparatus and an apparatus for tomosynthesis imaging according to an exemplary embodiment of the present invention.

  The X-ray medical imaging system 300 may include a mammography apparatus 200 and an apparatus 100 for tomosynthesis imaging. According to a further exemplary embodiment of the present invention, contrary to FIG. 3, an apparatus for tomosynthesis imaging may be integrated into the mammography apparatus 200. Furthermore, in contrast to the representation of FIG. 3, the medical imaging system 300 may further comprise an operator's computer or control terminal. The mammography device 200 may have a mechanical compression unit that may include two plates to compress the breast during mammography or biopsy.

  During the procedure, the breast is compressed using a dedicated mammography device. The parallel plate compression of the mechanical compression unit reduces the thickness of the tissue through which X-rays must pass, reduces the amount of scattered radiation (scattering reduces image quality), reduces the required radiation dose, and moves Flatten breast tissue thickness to improve image quality by holding a breast still to prevent blur. Diagnostic mammography can include the cranial tail, mid-horizontal and other views, including geometrically magnified and point-compressed views of a particular region of interest.

  4-6 shows the decomposition of the spectral mammography data, and FIG. 4 shows a two-dimensional projection image for explaining the present invention. In FIG. 4, mammogram data is measured over at least two different energy ranges. FIG. 5 shows the decomposition of the spectral mammogram into height images, the values given in mm. FIG. 6 illustrates glandular images also obtained by spectral decomposition and shows the percentage of glandular tissue.

  According to a further exemplary embodiment of the present invention, height information is used and taken from different angles to calculate a three-dimensional breast shape.

  FIGS. 7-9 show a backprojection method for illustrating the present invention, showing a cross section through the tomosynthesis image volume, with the main x-ray directions from top to bottom.

  FIG. 7 shows tomosynthesis reconstruction of a cross section through an elliptical object, eg, a breast shaded with dark gray. The spatial extent of the object cannot be reconstructed in the main x-ray direction, resulting in artifacts, where x-rays are represented by light gray areas, but also by artifacts within the object . FIG. 8 shows a reconstruction using a binary mask obtained only by identification of background rays that can reduce artifacts. FIG. 9 shows the reproducibility of using the binary mask generated from the geometric model with the spectral height image in FIG. The configuration is shown.

  The term “binary spectral tomosynthesis” refers to the reconstruction of a binary three-dimensional volume that represents the spatial extent of an object using spectral mammographic projection images.

  In another exemplary embodiment of the present invention, a computer program or computer program element adapted to perform the method steps of the method according to any of the previously described embodiments in a suitable system is provided.

  According to a further exemplary embodiment of the present invention, the computer program element is therefore stored on a computer device that can also be part of an embodiment of the present invention. The computing device may be adapted to perform or guide the execution of the method steps described above.

  The computer device is also adapted to operate the components of the device described above. The computing device can be adapted to operate automatically and / or execute user instructions. The computer program may be loaded into the working memory of the data processor. Thus, the data processor may be equipped to perform the method of the present invention.

  This exemplary embodiment of the present invention covers both a computer program that uses the present invention from the beginning and a computer program that, by update, turns an existing program into a program that uses the present invention.

  Further, the computer program element can provide all the steps necessary to satisfy the procedure of the exemplary embodiment of the method described above.

  According to a further exemplary embodiment of the present invention, a computer readable medium such as a CD-ROM is presented, the computer readable medium having computer program elements stored thereon, The computer program elements are described in the previous paragraph.

  The present invention can be used for X-ray tomosynthesis in different medical fields, for example breast imaging, breast imaging or dental imaging. The computer program is not only stored and / or distributed on an appropriate medium, such as an optical storage medium or other hardware or as a solid medium supplied as part, but also on the Internet, other wired or wireless communication systems, etc. You may distribute in other forms via.

  However, the computer program may be provided via a network such as the World Wide Web and downloaded from such a network into the working memory of the data processor.

  According to a further exemplary embodiment of the present invention, a medium is provided that makes it possible to download a computer program element, the computer program element performing a method according to any of the previously described embodiments of the present invention. Configured to do.

  It should be noted that embodiments of the present invention have been described with reference to various subject matters. In particular, some embodiments have been described with reference to method claims, while other embodiments have been described with reference to apparatus claims.

  However, unless otherwise indicated, one of ordinary skill in the art would consider any combination between features on different subjects as well as any combination of features belonging to one type of subject matter to be disclosed herein. Will be inferred from the above and following descriptions. However, all features can be combined to provide a greater synergy than a simple sum of features.

  Although the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments will be understood and attained by those skilled in the art in carrying out the claimed invention, from a study of the drawings, the disclosure of the specification, and the dependent claims. be able to.

  In the claims, the term “comprising” does not exclude other elements or steps, and the indefinite article “a, an” excludes a plurality. is not. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims (13)

An apparatus for tomosynthesis imaging, the apparatus comprising:
A mask generator module configured to generate a binary mask based on a geometric three-dimensional model of the scanned object derived from laser scanning of the object;
An image capture module configured to scan a series of two-dimensional projection images of the object;
During reconstruction of a three-dimensional image volume from the scanned series of two-dimensional projection images, the generated binary mask is applied so that the range of the reconstructed image volume is the range of the geometric model And an image processing module configured to limit to.   The mask generator module generates the binary mask based on the geometric model derived from image analysis of at least one 2D projection image of the scanned series of 2D projection images of the object. The apparatus for tomosynthesis imaging according to claim 1, configured to:   The tomosynthesis imaging of claim 2, wherein the mask generator module is configured to determine the geometric model of the object based on an intensity profile of at least one two-dimensional projection image of the object. Equipment for.   The image capture module can collect energy-resolved x-ray images, and the geometric model is derived from a quantitative height model obtained from spectral material decomposition using the energy-resolved two-dimensional projection image. The apparatus for tomosynthesis imaging according to any one of claims 1 to 3.   5. The tomosynthesis imaging according to claim 1, wherein the mask generator module is configured to generate the binary mask using an object thickness value measured by a mechanical compression unit. apparatus.   6. The image processing module according to any of claims 1 to 5, wherein the image processing module is configured to apply the generated binary mask during a reconstruction procedure of the scanned series of two-dimensional projection images. A device for tomosynthesis imaging.   An X-ray medical imaging system comprising the tomosynthesis imaging apparatus and mammography apparatus according to any one of claims 1 to 6. A method for tomosynthesis imaging comprising:
-Generating a binary mask based on a geometric model of the scanned object, derived from laser scanning of the object;
Scanning a series of two-dimensional projection images of the object;
Applying the generated binary mask to the scanned series of two-dimensional projection images to limit the extent of each of the images to the dimensions of the geometric model.   Generating the binary mask based on the geometric model further comprises deriving from image analysis of at least one 2D projection image of the scanned series of 2D projection images of the object. A method for tomosynthesis imaging according to claim 8.   Generating the binary mask based on the geometric model further comprises determining the geometric model of the object based on an intensity profile of at least one two-dimensional projection image of the object. A method for tomosynthesis imaging according to any of claims 8 to 9.   The step of generating the binary mask based on the geometric model further collects energy-resolved X-ray images, the geometric model being obtained quantitatively from spectral material decomposition of the energy-resolved two-dimensional projection image. The method for tomosynthesis imaging according to any of claims 8 to 10, derived from a height model.   12. The method of claim 8, wherein generating the binary mask based on the geometric model further comprises deriving a geometric model using an object thickness value measured by a mechanical compression unit. A method for tomosynthesis imaging according to any of the above.   The method for tomosynthesis imaging according to any of claims 8 to 12, wherein the method further comprises the step of generating a binary mask during a reconstruction procedure using the scanned series of two-dimensional projection images. Method.

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